where \(u = c\psi (4x-3)\)  is a linear transformation of the standard bump function (the one-dimensional analogue of (REF )), scaled by a constant \(c\)  so that its integral over \(\mathbb {R}\)  is equal to 1. As observed in [1]}, it is straightforward to check from (REF ) that \(h(x,y)\ll x^{-1}\)  and \(h(x,y)=0\)  whenever \(x> \max (1,2|y|)\) .
